Therefore we can deduce a subsidiary theorem about the homogeneous field structure.

##### Homogeneous field structure theorem

*Every homogeneous field of n*^{th} level consists of three homogeneous fields of n-1^{th} level.

Analogously we can proceed to achieve higher levels and this can be considered the basic concept of the construction of a homogeneous field of theoretically any level whatsoever.

#### 4. Portal network

If we forget about the fields, the portals and links we are left with form the so called portal network of the homogeneous field. This simplified network, which also disregards the link orientation, is used primarily as the first step in constructing a field over actual portals out in the field. The portal network concept also allows us to grasp the whole subject matter and comprehend its fundamentals.

##### Definition

Portal network is an organized set of portals and unoriented links of the homogeneous field.

Using the portal network and keeping in mind the previously mentioned information of homogeneous field structure we can now easily demonstrate how to create the basis of a level 4 homogeneous field (L4 HCF) using the so called **triangle method**.